Yes, you can connect to a mobile hotspot. The tablet supports the connection to Wi-Fi networks, including hotspots from other devices, via the Wi-Fi settings.
This means that if you activate a mobile hotspot on another device, you can connect to this Wi-Fi network on the tablet.
The USB-C port of the Redmi Pad SE does not support a video output as with USB-C 3.1. The tablet has a USB-C 2.0 port that does not enable display output via HDMI or DisplayPort. To connect to a TV or monitor, you would have to use the screen mirroring function as an alternative.
I have recorded FM recordings of the tablet with the microphone of another Pad SE and can't tell any difference. I can't judge the higher frequencies as I can no longer hear them.